Styrene resins, which are manufactured and commercially available under the name of HIPS, ABS etc., are excellent in appearance, mechanical properties and molding flowability, and therefore used in various fields such as vehicle components, electrical appliances, miscellaneous goods, etc.
Since these styrene resins are thermoplastic materials, however, the use of them is restricted in electrical and electronic equipment that is required to have flame retardance such as the self-extinguishing properties (V-0, V-1, and V-2 classes) according to U.S. Underwriters Laboratories (UL) Standard 94.
The flame retardance is provided by using halide compounds such as tetrabromobisphenol A (TBBA) and decabromodiphenylether (DBDE), a combination of halides and antimony compounds, or various phosphorous compounds.
Although the addition of these compounds can provide the flame retardance, an increase in the used amount of such expensive fire retardants leads to not only an increase in cost but also a significant deterioration in the physical properties such as impact resistance, which is one of the distinctive properties of the styrene resins. In addition, antimony trioxide, which is used in combination of the halide compounds, is a material of concern about environmental pollution. Therefore, some cases require the flame-retardant resin materials to be free of the antimony compound.
In some uses of the flame-retardant resin materials, such as household electrical appliances, OA, and electrical and electronic equipment, some components are required to have an electromagnetic wave-shielding property (EMI shielding property). In most of such uses, the resin materials are subjected to a secondary process such as plating, conductive coating, or the like, before used. Some electromagnetic wave-shielding thermoplastic resins are commercially available, including thermoplastic resins that contain the additive for increasing electrical conductivity, such as carbon fiber, carbon black, and stainless steel fiber. However, no thermoplastic resin is available to satisfy all of flame retardance, electromagnetic wave-shielding stability, and good molding appearance.
The present invention has been made to solve the above problems. It is therefore an object of the present invention to provide a flame-retardant and electromagnetic wave-shielding, thermoplastic resin composition that has excellent flame retardance, good appearance, and excellent molding flowability.
The inventors have made active investigations in light of the above problems and have found that the use of a specific flame retardant, a metal-coated fiber, and a specifically shaped filler in a specific amount range of composition can provide a flame-retardant and electromagnetic wave-shielding, thermoplastic resin composition with excellent flame retardance, good appearance, and excellent molding flowability, and have finally made the present invention.